1. Field of the Invention
The present invention relates to motor vehicle seats and, more particularly, is concerned with a motor vehicle seat having a backrest foldable between an erected seating position and a folded sleeping position and a seat cushion normally disposed in a retracted seating position and being mechanically coupled to the backrest such that the folding of the backrest from the erected seating position to the folded sleeping position causes displacement of the seat cushion from the retracted seating position to an extended sleeping position in which the seat cushion is substantially aligned with the backrest in the folded sleeping position.
2. Description of the Prior Art
German Patent Document No. DE 32 22 273 A1 discloses a latching mechanism for a motor vehicle seat. The seating portion of this motor vehicle seat is supported on the motor vehicle floor on the front end of the seating portion via arms provided on both sides. Each of these arms has a vertically disposed slot in which is guided a pin mounted stationary on the seating portion. Each pin is normally held in an upper position of the respective slot by a catch pivotally mounted on the respective arm and disposed in a closing position. Each catch is prestressed to the closing position through action of a biasing force imposed by a tension spring and connected via a wire with a backrest of the motor vehicle seat. When the backrest is folded back, sufficient tension is exerted on each of the wires to overcome the biasing force of the tension springs and pivot the catches such that the pins are released and can glide downwardly in the slots of the arms. This changes the seating portion into a lowered position either by its own weight or by pressure from above on its front end. In the lowered position the seating portion is substantially aligned in contact on the backrest which is completely folded back.
One disadvantage of this solution is that the required latching mechanism is structured in a rather complicated manner. Another disadvantage is that the seating portion is not necessarily lowered in view of the absence of the application of any positive force, such as generated directly through the folding of the backrest, but rather is lowered only under the effect of gravity or by the application of additional external forces.
In German Patent Document No. DE 92 04 215 U1 a folding seat bench for mobile homes is described. This bench comprises a box-form seat frame supporting a seating portion and which, as is customary in mobile homes, can be used as storage space. A backrest frame is carried in the seat frame on the motor vehicle floor and therein locked at lower supports of the seat frame. The backrest frame is supported on the back wall of the seat frame. First guide bars are provided having lower ends secured by pivots at lower supports provided on both sides of the seat frame and also having upper ends connected via pivots with the backrest frame. In addition, two further guide bars are provided having upper ends fastened with a seat cushion and also having lower ends secured by pivots on the backrest frame. After releasing the latching of the backrest frame, it can be pivoted forward together with the guide bars and thereby the seat cushion is simultaneously displaced forwardly. At the completion of this motion by the backrest frame, in which it is simultaneously or subsequently folded rearwardly about its pivot with the first guide bars, its upholstery forms together with the seat cushion a substantially level resting surface. The kinematics of the motion system, comprised by the backrest frame and first and second guide bars, do not necessarily take place in view of the absence of the application of any positive force, so that this folding seat bench is not user-friendly.